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Browsing by Author "Madgwick, H. A. I."

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    Hymenopterous parasites of lps spp. bark beetles (Coleoptera:Scolytidae) in Virginia
    Berisford, C. Wayne (Virginia Tech, 1968-06-19)
    The pine engraver beetles (~ spp.:Coleoptera:Scolytidae) may be serious pests depending on certain prerequisite conditions. In their secondary or "normal" role they breed in slash and damaged, dying, and dead trees. The broods emerging from these sources normally attack similar material. When such material is scarce due to cessation of cutting operations in mid-season or when conditions are especially favorable for brood development, an excess of beetles is often produced which, due to the lack of more suitable material, attack healthy trees. Repeated attacks cause these trees to succumb and die. When normally healthy trees are weakened by fire, flood, defoliation, drought, stagnation, etc., then they become more acceptable host material for successful engraver attacks. When the production of a very large number of beetles in "normal" breeding material coincides with physiological stress in "healthy" trees, then population explosions can occur. When large numbers of beetles and low host vigor do not coincide, spot kills cornnon1y occur. According to Thatcher (32), spot kills, although not conspicuous, add up to large volumes of timber loss each year.
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    Nantucket pine tip moth infestations in relation to stand type
    Berisford, C. Wayne (Virginia Tech, 1966-02-05)
    The Nantucket pine tip moth, Rhyacionis frustrana (Comstock) Is a common pest of young pines. In the eastern United States all species of yellow pines are attacked to some degree except longleaf pine, Pinus palustrla Mill. (Yates 1960). Chemical control of the tip moth has been demonstrated to be effective, but It generally has been considered to be too expensive since the evidence was only Inconclusive as to any permanent additional height growth of pines resulting from complete control. There has been considerable speculation about silvicultural control and a number of methods have been suggested by various workers. Many of these methods, however, have not been backed by quantitative data. Some of the suggested silvicultural controls are mixing susceptible species with resistant species, starting. trees under an overstory, using close spacing, and starting trees In brush. To date, there have been no detailed investigations of silvicultural control for the tip moth. This study was designed to determine if stands of loblolly pine, Pinus taeda L., growing under various conditions show any differences in rate of attack by the tip moth that might, In the future, be a basis for silvicultural or integrated control.
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    On Estimating the Aboveground Weights of Tree Stands
    Madgwick, H. A. I.; Satoo, T. (Ecological Society of America, 1975)
    Simulated sampling of nine tree stands was used to compare estimated stand component weights with known weights based on complete harvest. On average, estimates based on regressions of logarithm weight on either logarithm tree diameter or on logarithm (diameter)2 x height overestimated weights of stems, branches, and leaves by - 3% when the inherent bias of such regressions was accounted for. Ninety-five percent confidence intervals based on random sampling encompassed the measured stand weights 79%-100% of the time. Similar confidence intervals using stratified random sampling based on tree diameter encompassed the measured stand weights only 44%-98% of the time. The small average bias in estimates of stand weight using logarithmic regressions is of minor importance compared with the variation in estimates among replicated samples.